The present invention relates to a positive type photosensitive resin composition, which is suitable for using in electric or electronic devices, particularly in semiconductor devices, and which is developable by an alkaline aqueous solution.
Currently, polyimide has been used widely in the field of semiconductor manufacture, which requires strict reliability, because polyimide is superior in heat-resistance, mechanical strength, and electrical insulation to other materials.
The utilization of polyimide as a passivation film, a buffer-coating film an .alpha.-ray shielding film an insulating film between layers, and so on in the semiconductor field is well known. In case of the utilization, a process for manufacturing fine through-holes in the polyimide film is necessary for forming a path through the upper and the lower conductive layers, or for connecting an external lead wire. Therefore, generally, a chemical etching treatment of the polyimide film using a photoresist is performed.
However, pattern formation of the polyimide film requires application and stripping of the photoresist, and the series of process steps is complex. Therefore, a photosensitive polyimide, which is capable of being formed by a short process and of being manufactured finely, has been required. As the results of extensive developing efforts devoted by many manufacturers to respond this requirement, a negative type photosensitive polyimide, which can be developed in an organic solvent, came to be commercialized. However, currently, in view of the high efficiency of the facility and current global environmental problems, a positive type photosensitive polyimide, which can not be developed in an organic solvent, but requires an alkaline aqueous solution, has come to be required.
A positive type photosensitive polyimide can be divided into two categories including, in which a photosensitive group is introduced into the polyimide precursor (JP-B-1-59571 (1989)), and another to which a photosensitive group is added. As for the latter positive type photosensitive polyimide of the photosensitive group addition type, one composed of o-quinonediazidesulfonic acid ester (JP-A-4-168441 (1992), JP-A-4-204738 (1992)), which generates carboxylic acid by light irradiation, and one composed of a polyimide precursor added with dihydroxypyridine derivatives (JP-A-6-43648 (1994)), and others have been disclosed. However, all of the above photosensitive imide have problems in resolution, sensitivity, and so on. The above o-quinonediazidesulfonic acid ester is a photosensitive agent used as a photoresist, and both a dissolution hindrance effect in the unexposed region and a dissolution enhancing effect in the exposed region as the photosensitive agent of the polyimide precursor are insufficient.
Particularly, the positive type photosensitive polyimide had a special problem, which did not exist in the negative type, such that the unexposed region was corroded at its substrate portion in the developing process, because the exposed region was dissolved when the positive type was used. As countermeasures for the problem, a method of mixing a silan group coupling agent such as 3-aminopropylmethoxysilan into the photosensitive resin composition, and a method improving the adhesiveness at the development by using a surface treated substrate are well known. However, in the case of a semiconductor, such a surface treatment is impossible, and the mixing of a coupling agent with the photosensitive resin composition is also not so effective.
As explained above, various attempts to add a photosensitivity of the positive type to the polyimide which can be developed by an alkaline aqueous solution have been performed, but sufficient results could not be obtained.